| Year | Value | | 2021 | 6,435 | | 2020 | 6,464 | | 2019 | 6,384 | | 2018 | 6,413 | | 2017 | 6,440 | | 2016 | 5,520 | | 2015 | 5,339 | | 2014 | 5,377 | | 2013 | 5,203 | | 2012 | 5,262 | | 2011 | 5,170 | | 2010 | 5,045 | | 2009 | 5,226 | | 2008 | 5,156 | | 2007 | 5,181 | | 2006 | 5,088 | | 2005 | 5,145 | | 2004 | 5,135 | | 2003 | 5,510 | | 2002 | 5,630 | | 2001 | 5,610 | | 2000 | 5,660 | | 1999 | 5,590 | | 1998 | 5,620 | | 1997 | 5,630 | | 1996 | 5,640 | | 1995 | 5,730 | | 1994 | 5,790 | | 1993 | 5,770 | | 1992 | 5,770 | | 1991 | 5,780 | | 1990 | 5,790 | | 1989 | 5,750 | | 1988 | 5,760 | | 1987 | 5,770 | | 1986 | 5,790 | | 1985 | 5,750 | | 1984 | 5,640 | | 1983 | 5,530 | | 1982 | 5,400 | | 1981 | 5,380 | | 1980 | 5,330 | | 1979 | 5,330 | | 1978 | 5,330 | | 1977 | 5,310 | | 1976 | 5,300 | | 1975 | 5,400 | | 1974 | 5,450 | | 1973 | 5,370 | | 1972 | 5,270 | | 1971 | 5,270 | | 1970 | 5,250 | | 1969 | 5,230 | | 1968 | 5,210 | | 1967 | 5,250 | | 1966 | 5,250 | | 1965 | 5,140 | | 1964 | 5,250 | | 1963 | 5,220 | | 1962 | 5,050 | | 1961 | 5,110 |
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